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The 10 Most Important Questions In Science*

I noticed in The Guardian that there's a book coming out this week listing the 20 biggest challenges for modern science. I'd like to go over 10 of them today, perhaps coming back to the other 10 next week.

*Every list of "most important questions" comes freighted with a certain amount of arbitrariness and The Big Questions in Science: The Quest to Solve the Great Unknowns by Mun Keat Looi, Hayley Birch and Colin Stuart is no different. However, I have to admit that this list encompasses some of the most difficult and intriguing open scientific questions, including some that go to the heart of the current debate on scientism. (Our very own Adam Frank visited that theme recently.) So, without further preface, here are the 10 big questions for this week:

What is the universe made of? We know only 5 percent of the composition of the universe. This 5 percent is made of the familiar atoms of the periodic table, their molecular aggregates or of the components of atoms, protons, electrons and neutrons. There are also neutrinos, the elusive particles that can traverse matter as if nothing were there, including the whole of Earth. The mystery is the other 95 percent, composed of dark matter (roughly at 25 percent) and dark energy (roughly at 70 percent). Dark matter doesn't shine and is found around galaxies and clusters of galaxies, like an invisible cloak. We know it's there because it has mass and hence gravity: It pulls on the familiar 5 percent and we can measure this effect. Dark energy is much more mysterious, a kind of ether-like medium filling up space with the bizarre property of pushing it apart, making galaxies accelerate from one another. We don't know what either dark matter or dark energy are, and there are hypothetical explanations that try to modify Einstein's theory of gravity to accommodate the observations and do away with the darkness.

How did life come about? Life appeared on Earth some 3.5 billion years ago, perhaps earlier. The mystery here is how aggregates of nonliving atoms gathered into progressively more complex molecules that eventually became the first living entity, a chemical machine capable of metabolism and reproduction.

Are we alone in the universe? This question is really two questions: Does life exist out there and, if so, what fraction of this alien life is complex and intelligent? If intelligent life is not so rare, why haven't we heard from "them" yet? I recommend the book by Lee Billings, Five Billion Years of Solitude, for an up-to-date synopsis of the search for life elsewhere and the key people behind it.

What makes us human? We have three times more neurons than a gorilla, but our DNAs are almost identical. Many animals have a rudimentary language, can use tools and recognize themselves in mirrors. So, what is it that differentiates us from them? The thicker frontal cortex? The opposing thumb? The discovery of fire and the ability to cook? Our culture? When did language and toolmaking appear? (Barbara King recently offered her take on this topic.)

What is consciousness? We've been there before in these pages, wondering about the nature of consciousness. How is it that the brain generates the self of self, the unique experience that we have of being ... unique? Can the brain be reversed-engineered to be modeled by machines? Or is this a losing proposition? And why is there a consciousness at all? What is its evolutionary purpose, if any?

Why do we dream? Even though we spend about a third of our lives sleeping, we still don't know why we dream. Do dreams have an essential function, physiological and or psychological? Or are they simply random images of a brain in partial rest? Was Freud right about his theory that dreams are some sort of expression of repressed desires? Or is that all bogus?

Why does matter exist? According to the laws of physics, matter shouldn't exist on its own; each particle of matter, each electron, proton, neutron, should have a companion of antimatter, like twins. So, there should be positrons, antiprotons and antineutrons in abundance. But there aren't. The problem is that when matter and antimatter meet, they disintegrate in a puff of high-energy radiation. If you shook hands with your antimatter other, a good chunk of the United States would blow up in smoke. So, the mystery is what happened to this antimatter. Clearly, if the universe had equal amounts of both earlier on, something happened to favor matter over antimatter. What? Was the universe "born" this way, with a huge asymmetry between matter and antimatter? Maybe some primordial asymmetry evolved to do the job, selecting matter? If so, when did it act in the cosmic history? And what would this asymmetry be?

Are there other universes? Or is our universe the only one? Believe it or not, modern theories of cosmology and particle physics predict the existence of other universes, potentially with different properties to our own. Are they there? How would we know, if we could? If we can't confirm this hypothesis, is it still part of science?

Where will we put all the carbon? With the global ramping up of industrialization, we are putting more and more carbon up in the atmosphere, accelerating global warming. What can be done to change our impact on the environment? And what happens if we don't? Models of global warming have a range of predictions, from somewhat mild to dire. Should we bet on the low odds that doing nothing will be OK? Or is it time to really take this seriously at a global scale, for the benefit of the next generation?

How can we get more energy from the sun? We have based our explosive growth mainly on fossil fuels. Nevertheless, we have a remarkable source of energy up in the sky, waiting to be exploited more efficiently. Also, can we reproduce the solar engine here on Earth, fusing hydrogen into helium in a controllable and viable source of energy, solving our energy problem for the foreseeable future?

Those are, indeed, some of The Big Questions in Science. They run from the abstract to the applied and should speak to most of us in one way or another.

You can keep up with more of what Marcelo is thinking on Facebook and Twitter: @mgleiser

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